1. Field of the Invention
The present invention relates to an improved ankle-foot orthosis for supporting the foot and ankle of a user. The orthosis of the present invention assists the user in plantar flexion and/or dorsiflexion extension of the user's foot while simultaneously controlling medial and lateral ankle stiffness as well as torsion of the ankle in the coronal plane.
2. Discussion of Related Art
Presently available ankle-foot orthoses are limited, because the orthoses cannot be customized to specifically address a specific user's dorsiflexion and plantar flexion stiffness needs to any significant or acceptable degree. The dorsiflexion stiffness of current orthoses is generally constant or decreases with increasing ankle angle, that is, the angle between a line passing between a user's knee and ankle and a horizontal line also passing through the ankle, as the foot dorsiflexes. The dorsiflexion stiffness of a normal human foot increases dramatically with increasing ankle angle. As a result, for users needing an orthosis that matches the dorsiflexion stiffness of the normal human foot, the presently available orthoses are unsatisfactory, leaving some users with reduced mobility and a decreased quality of life.
A further drawback of current orthoses relates to plantar flexion stiffness. An orthosis having low plantar flexion stiffness allows many users to walk more easily. However, currently available orthoses, other than some articulated orthoses, have a plantar flexion that is much higher, making walking and general mobility more difficult, and decreasing the user's quality of life. Additionally, dorsiflexion and plantar flexion stops, those features that prevent the orthoses from moving beyond a certain point in dorsiflexion and plantar flexion, respectively, provided in the presently available orthoses are rigid. Consequently, the stops cause the transmission of large forces into the user's body when the stops engage, and, over time, the relatively large forces damage a user's knee and hip joints.